References
Correll, David L. 1986. Watershed research perspectives. Washington, DC: Smithsonian Institution Press.
Everest, F.H.; Harr, D.H. 1982. Influence of forest and rangeland management on anadromous fish habitat in Western North America. Silvicultural treatments. Gen. Tech. Rep. PNW-134. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station.
Hill, A.R. 1983. Denitrification: it's importance in a river draining an intensively cropped watershed. Agriculture, Ecosystems and Environment. 10: 47-62.
Jacobs, T.C.; Gilliam, J.W. 1985. Riparian losses of nitrate from agricultural drainage waters. Journal of Environmental Quality. 14(4): 467-472.
Karr, James R. 1990. Bioassessment and nonpoint source pollution: An overview. In: second national symposium on water quality assessment. Meeting summary. Washington, DC: U.S. Environmental Protection Agency, Office of Water: 4-1-4-18.
Karr, J.R.; Schlosser, I.J. 1978. Water resources and the land water interface. Science. 201: 229-334.
Lowrance, Richard; Leonard, Ralph; Sheridan, Joseph. 1985. Managing riparian ecosystems to control nonpoint pollution. Journal of Soil and Water Conservation. 40(1): 87-91.
Lowrance, Richard; Todd, Robert L.; Fail, Joseph, Jr.; Hendrickson, Ole, Jr.; Leonard, Ralph; Asmussen, Loris. 1984. Riparian forests as nutrient filters in agricultural watersheds. BioScience. 34(8): 374-377.
McCormick, J.H.; Hokanson, K.E.F.; Jones, B.R. 1972. Effects of temperature on growth and survival of young brook trout, Salvelinus fontinalis. Journal of the Fisheries Research Board of Canada. 29: 1107-1112
Norris, L.A.; Lorz, H.W.; Gregory, S.V. 1983. Influence of forest and rangeland management on anadromous fish habitat in Western North America. Forest chemicals. Gen. Tech. Rep. PNW-149. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station.
Peterjohn, William T.; Correll, David L. 1983. Nutrient dynamics in an agricultural watershed: Observations of the role of a riparian forest. Ecology. 65(5): 1466-1475.
Rajagopal, R.; Tobin, Graham. 1989. Expert opinion and groundwater quality protection: The case of nitrate in drinking water. Ground Water. 27(6): 835-847.
Raleigh, R.F.; Hickman, T.J.; Nelson, K.L.; Maughan, O.E. 1980. Riverine habitat evaluation procedures for rainbow trout. In: Proceedings of the trout stream improvement workshop; 1980 November; Asheville, NC. Place of Publication unknown, USDA Forest Service and Trout Unlimited: 50-59.
Richardson, Curtis J. 1988. Freshwater wetlands: Transformers, filters or sinks? Forem. 11(2): 3-9.
Salo, Ernest 0.; Cundy, Terrance, W. 1987. Streamside management: Forestry and fishery interactions. Contrib. No. 57. Seattle, WA: University of Washington, Institute of Forest Resources.
Schlosser, Isaac J.; Karr, James R. 1981. Riparian vegetation and channel morphology impact on spatial patterns of water quality in agricultural watersheds. Environmental Management. 5(3): 223-243.
Schnabel, Ronald R. 1986a. Nitrate concentration in a small stream affected by chemical and hydrological interactions in the riparian zone. In: Watershed research perspectives. Washington, DC: Smithsonian Institution Press: 263-282.
Schnabel, Ronald R. 1986b. Nitrate contamination of ground water in an upland Pennsylvania watershed. In: Proceedings of a conference on the agricultural impacts on ground water; 1986 August; Omaha, NE. Dublin, Ohio. National Water Well Association: 352-380.
Wolverton, B.C. 1988. Aquatic plants for pH adjustments and removal of toxic chemicals and dissolved materials from water supplies. Journal of the Mississippi Academy of Sciences. XXXIII: 71-80.
SPECIFICATION/RIPARIAN FOREST BUFFER
Requirements
Runoff and wastewater to be buffered or filtered by Zone 1 will be limited
to sheet flow or subsurface flow only. Concentrated flows must be converted
to sheet flow or subsurface flows prior to entering Zone 1. Outflow from subsurface
drains must not be allowed to pass through the riparian forest in pipes or
tile thus circumventing the treatment processes. Subsurface drain outflow
must be converted to sheet flow for treatment by the riparian forest buffer
or treated elsewhere in the system prior to entering the surface water.
Dominant vegetation will be composed of a variety of native riparian tree
and shrub species and such plantings as necessary for stream bank stabilization
during the establishment period. A mix of species will provide the prolonged
stable leaf fall and variety of leaves necessary to meet the energy and pupation
needs of aquatic insects.
Large over-mature trees are valued for their detritus and large woody debris
contributions to the stream ecosystem. Therefore, management of Zone 1 will
be limited to bank stabilization and removal of potential problem vegetation.
Occasional removal of extreme high value trees may be permitted where water
quality values are not compromised. Logging and other overland equipment shall
be excluded except for stream crossings and stabilization work.
Livestock will be excluded from Zone 1 except for designed stream crossings.
Zone 2
Location
Zone 2 will begin at the edge of Zone 1 and occupy an additional strip of land with a minimum width of 60 feet measured horizontally in the direction of flow. Total minimum width of Zones 1 & 2 is therefore 75 feet. Note that this is the minimum width of Zone 2 and that the width of Zone 2 may have to be increased as described in the section "Determining the Total Width of Buffer" to create a greater combined width for Zones 1 & 2.
Purpose
The purpose of Zone 2 is to provide necessary contact time and carbon energy source for buffering processes to take place and to provide for long term sequestering of nutrients in the form of forest trees. Outflow from subsurface drains must not be allowed to pass through the riparian forest in pipe or tile thus circumventing the treatment processes. Subsurface drain out flow must be converted to sheet flow for treatment by the riparian forest buffer or treated elsewhere in the system prior to entering the surface water.
Requirements
Runoff and wastewater to be buffered or filtered by Zone 2 will be limited to sheet flow or subsurface flow only. Concentrated flows must be converted to sheet flow or subsurface flows prior to entering Zone 2.
Predominant vegetation will be composed of riparian trees and shrubs suitable to the site, with emphasis on native species and such plantings as necessary to stabilize soil during the establishment period. Nitrogen fixing species should be discouraged where nitrogen removal or buffering is desired. Species suitability information should be developed in consultation with state and federal forestry agencies, Soil Conservation Service, and Fish and Wildlife Service.
Specifications should include periodic harvesting and timber stand improvement (TSI) to maintain vigorous growth and leaf litter replacement and to remove nutrients and pollutants sequestered in the form of wood in tree boles and large branches. Management for wildlife habitat, aesthetics, and timber are not incompatible with riparian forest buffer objectives as long as shade levels and production of leaf litter, detritus and large woody debris are maintained. Appropriate logging equipment recommendations shall be determined in consultation with the state and federal forestry agencies.
Livestock shall be excluded from Zone 2 except for necessary designed stream crossings.
Zone 3
Location
Zone 3 will begin at the outer edge of Zone 2 and have a minimum width of 20 feet. Additional width may be desirable to accommodate land shaping and mowing machinery. Grazed or ungrazed grassland meeting the purpose and requirements stated below may serve as Zone 3.
Purpose
The purpose of Zone 3 is to provide sediment filtering, nutrient uptake and the space necessary to convert concentrated flow to uniform, shallow, sheet flow through the use of techniques such as grading, and shaping, and devices such as diversions, basins and level lip spreaders.
Requirements
Vegetation will be composed of dense grasses and forbs for structure stabilization, sediment control and nutrient uptake. Mowing and removal of clippings is necessary to recycle sequestered nutrients, promote vigorous sod and control weed growth.
Vegetation must be maintained in a vigorous condition. The vegetative growth must be hayed, grazed or otherwise removed from Zone 3. Maintaining vigorous growth of Zone 3 vegetation must take precedence and may not be consistent with wildlife needs.
Zone 3 may be used for controlled intensive grazing when conditions are such that earthen water control structures will not be damaged.
Zone 3 may require periodic reshaping of earth structures, removal or grading of accumulated sediment and reestablishment of vegetation to maintain effectiveness of the riparian buffer.
Determining need for protection
Buffers should be used to protect any body of water which will not be: treated by routing through a natural or artificial wetland determined to be adequate treatment; treated by converting the flow to sheet flow and routing it through a forest buffer at a point lower in the watershed.
Determining total width of the buffer
Note that while not specifically addressed, slope and soil permeability are components of the following buffer width criteria.
Each of the following criteria is based on methods developed or used by persons conducting research on riparian forests.
Streamside Buffers
The minimum width of streamside buffer areas can be determined by any of several
methods suitable to the geographic area.
1) Based on soil hydrologic groups as shown in the county soil survey report,
the width of Zone 2 will be increased to occupy any soils designated as Hydrologic
Group D and those soils of Hydrologic Group C which are subject to frequent
flooding. If soils of Hydrologic Groups A or B occur adjacent to intermittent
or perennial streams, the combined width of Zones 1 & 2 may be limited
to the 75 foot minimum.
2) Based on area, the width of Zone 2 should be increased to provide a combined width of Zones 1 & 2 equal to one-third of the slope distance from the stream bank to the top of the pollutant source area. The effect is to create a buffer strip between field and stream which occupies approximately one-third of the source area.
3) Based on the Soil Capability Class of the buffer site as shown in the county soil survey, the width of Zone 2 should be increased to provide a combined width of Zones 1 & 2 as shown below.
| Capability Class | Buffer Width |
| Cap. I, II e/s, V | 75' |
| Cap. III e/s, IV e/s | 100' |
| Cap. VI e/s, VII e/s | 150' |
Pond and Lake-Side buffer strips
The area of pond or lake-side buffer strips should be at least one-fifth the drainage area of the cropland and pastureland source area. The width of the buffer strip is determined by creating a uniform width buffer of the required area between field and pond. Hydrologic Group and Capability Class methods of determining width remain the same as for streamside buffers. Minimum widths apply in all cases.
Environmentally Sensitive Wetlands
Some wetlands function as nutrient sinks and when they occur in fields or at field margins can be used for renovation of agricultural surface runoff and/or drainage. However, most wetlands adjoining open water are subject to periodic flushing of nutrient-laden sediments and, therefore, require riparian buffers to protect water quality.
Where open water wetlands are roughly ellipsoid in shape, they should receive the same protection as ponds.
Where open water wetlands exist in fields as seeps along hill slopes, buffers should consist of Zones 1, 2 & 3 on sides receiving runoff and Zones 1 & 3 on the remaining sides. Livestock must be excluded from Zones 1 & 2 at all times and controlled in Zone 3. Where Zones 1 & 3 only are used, livestock must be excluded from both zones at all times, but hay removal is desirable in Zone 3.
Vegetation Selection
Zone 1 & 2 vegetation will consist of native streamside tree species on soils of Hydrologic Groups D and C and native upland tree species on soils of Hydrologic Groups A and B.
Deciduous species are important in Zone 2 due to the production of carbon leachate from leaf litter which drives bacterial processes that remove nitrogen as well as to the sequestering of nutrients in the growth processes. In warmer climates evergreens are also important due to the potential for nutrient uptake during the winter months. In both cases a variety of species is important to meet the habitat needs of insects important to the aquatic food chain.
Zone 3 vegetation should consist of perennial grasses and forbs.
Species recommendations for vegetated buffer areas depend on the geographic location of the buffer. Suggested species lists should be developed in collaboration with appropriate state and federal forestry agencies, the Soil Conservation Service and the Fish and Wildlife Service. Species lists should include trees, shrubs, grasses, legumes, forbs, as well as site preparation techniques. Fertilizer and lime, helpful in establishing buffer vegetation, must be used with caution and are not recommended in Zone 1.
Maintenance Guidelines
General
Buffers must be inspected annually and immediately following severe storms for evidence of sediment deposit, erosion or concentrated flow channels. Prompt corrective action must be taken to stop erosion and restore sheet flow.
The following should be avoided within the buffer areas: excess use of fertilizers, pesticides, or other chemicals, vehicular traffic or excessive pedestrian traffic and removal or disturbance of vegetation and litter inconsistent with erosion control and buffering objectives.
Zone 1 vegetation should remain undisturbed except for removal of individual trees of extremely high value or trees presenting unusual hazards such as potentially blocking culverts.
Zone 2 vegetation, undergrowth, forest floor, duff layer and leaf litter shall remain undisturbed except for periodic cutting of trees to remove sequestered nutrient and to maintain an efficient filter by fostering vigorous growth, and for spot site preparation for regeneration purposes. Controlled burning for site preparation, consistent with good forest management practice could also be used in Zone 2.
Zone 3 vegetation should be mowed and the clippings removed as necessary to remove sequestered nutrient and promote dense growth for optimum soil stabilization. Hay or pasture uses can be made compatible with objectives of Zone 3.
Zone 3 vegetation should be inspected twice annually and remedial measures taken as necessary to maintain vegetation density and remove problem sediment accumulations.
Stable Debris
As Zone 1 reaches 60 years of age, it will begin to produce large stable debris. Large debris, such as logs create small dams which trap and hold detritus for processing by aquatic insects thus adding energy to the stream ecosystem, strengthening the food chain and improving aquatic habitat. Wherever possible, stable debris should be conserved.
Where debris dams must be removed, try to retain useful, stable portions which provide detritus storage.
Deposit removed material a sufficient distance from the stream that it will not be refloated by high water.
Planning Considerations
1. Evaluate the type and quantity of potential pollutants that will be derived
from the drainage area.
2. Select species adapted to the zones based on soil and site factors and
possible commercial goals such as timber and forage.
3. Plan to establish trees early in the dormant season for maximum viability.
4. Be aware of visual aspects and plan for wildlife habitat improvement, if
desired.
5. Consider provisions for mowing and removing vegetation from Zone 3. Controlled
grazing may be satisfactory in Zone 3 when the
filter area is dry and firm.
Definition
An area of trees and other vegetation located in areas adjoining and upgradient from surface water bodies and designed to intercept surface runoff, wastewater, subsurface flow and deeper groundwater flows from upland sources for the purpose of removing or buffering the effects of associated nutrients, sediment, organic matter, pesticides or other pollutants prior to entry into surface waters and groundwater recharge areas.
Scope
This specification establishes the minimally acceptable requirements for the reforestation of open lands and renovation of existing forest to be managed as Riparian Forest Buffers for the purposes stated.
Purpose
To remove nutrients, sediment, animal-derived organic matter, and some pesticides from surface runoff, subsurface flow and near root zone groundwater by deposition, absorption, adsorption, plant uptake, denitrification, and other processes, thereby reducing pollution and protecting surface water and groundwater quality.
Conditions Where Practice Applies
Subsurface nutrient buffering processes, such as denitrification, can take place in the soil wherever carbon energy, bacteria, oxygen, temperature and soil moisture are adequate. Nutrient uptake by plants occurs where the water table is within the root zone. Surficial filtration occurs anywhere surface vegetation and forest litter are adequate.
The riparian forest buffer will be most effective when used as a component
of a sound land management system including nutrient management and runoff,
sediment and erosion control practices. Use of this practice without other
nutrient and runoff, sediment and erosion control practices can result in
adverse impacts on buffer vegetation and hydraulics including high maintenance
costs, the need for periodic replanting and the carrying of excess nutrients
and sediment through the buffer by concentrated flows.
This practice applies on lands:
1) adjacent to permanent or intermittent streams which occur at the lower
edge of upslope cropland, grassland or pasture; 2) at the margins of lakes
or ponds which occur at the lower edge of upslope cropland, grassland or pasture;
3) at the margin of any intermittent or permanently flooded, environmentally
sensitive, open water wetlands which occur at the lower edge of upslope cropland,
grassland or pasture;
4) on karst formations at the margin of sinkholes and other small groundwater
recharge areas occurring on cropland, grassland or pasture.
Note: In high sediment production areas (8-20 in/ 100 yrs.), severe sheet,
rill and gully erosion must be brought under control on upslope areas for
this practice to function correctly.
Design Criteria
Riparian Forest Buffers
Riparian forest buffers will consist of three distinct zones and be designed to filter surface runoff as sheet flow and downslope subsurface flow which occurs as shallow groundwater. For the purposes of these buffer strips, shallow ground water is defined as saturated conditions which occur near or within the root zone of trees and other woody vegetation and at relatively shallow depths where bacteria, oxygen, and soil temperature contribute to denitrification. Streamside Forest Buffers will be designed to encourage sheet flow and infiltration and impede concentrated flow.
Zone 1
Location
Zone 1 will begin at the top of the stream bank and occupy a strip of land with a fixed width of fifteen feet measured horizontally on a line perpendicular to the streambank.
Purpose
The purpose of Zone 1 is to create a stable ecosystem adjacent to the water's edge, provide soil/water contact area to facilitate nutrient buffering processes, provide shade to moderate and stabilize water temperature encouraging the production of beneficial algal forms and to contribute necessary detritus and large woody debris to the stream ecosystem.
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